Posted
by
ScuttleMonkey
on Friday September 11, 2009 @01:57PM
from the best-easy-chair-ever dept.

sterlingda writes to tell us that scientists have built a mouse-levitating superconducting magnet, working on behalf of NASA to study variable levels of gravity. The group hopes to ascertain what physiological impacts prolonged exposure to microgravity might have. "Repeated levitation tests showed the mice, even when not sedated, could quickly acclimate to levitation inside the cage. After three or four hours, the mice acted normally, including eating and drinking. The strong magnetic fields did not seem to have any negative impacts on the mice in the short term, and past studies have shown that rats did not suffer from adverse effects after 10 weeks of strong, non-levitating magnetic fields."

Mr. A. Dumbledore, of Little Tweeting, England, writes to say "I fail to see why magnetic fields are necessary to levitate mice. I personally make them fly using a hand wave and the incantation 'sudo rodentus soarus'. Befuddling the owls sometimes, of course."

Ok... I know I should be more attentive but when I first read that headline I thought;

Scientists Levitate Miss USA

I personally believe that U.S. scientists are unable to do so because, um, some scientists out there in our nation don't have magnets and, uh, I believe that our, uh, research like such as, uh, Caltech and, uh, the Harvard and everywhere like such as, and I believe that they should, uh, our research over here in the U.S. should help the U.S., uh, should help Caltech and should help the Harvard and the Asian countries, so we will be able to build up our future.

For that matter, why does anyone think it's normal for humans to eat cow secretions?

Ah; now that's a more interesting one. Once upon a time it wasn't normal [bbc.co.uk] however, (almost certainly, unless you are a freak or are Chinese) you and your genetically dominant have been taking advantage of a recent gene mutation [scientificamerican.com] to make that normal.

What doesn't give energy/nutrition will kill if eaten exclusively. If you ate only grass for long enough, you would be dead. Just because it isn't in ten minutes, doesn't mean it falls on the not-dead side. Unless you adapt to digesting grass sufficiently before you stave to death.

Other researchers have made live frogs and grasshoppers float in mid-air before, but such research with mice, being closer biologically to humans, could help in studies to counteract bone loss due to reduced gravity over long spans of time, as might be expected in deep space missions or on the surfaces of other planets.

That isn't how it works. The same fieild intensity that levitates a mouse would levitate a person. However, the volume throughout which the field is of constant intensity would have to be scaled up and the energy stored in the field is proportional to volume so your number may not be too far off if seen as a measure of the size and cost of the magnet.

Wait? Wha? Highschool physics much? How was this post modded 5+ informative when it's so wrong?

With 16T, you can levitate an object of any size so long as it predominantly consists of water.
It's not like a 1g frog will float, but a 2g frog will fall in the same magnetic field. The reason why the things floated are small is because its easier to make small magnetic fields. If you have a current going around a loop, and you double the radius of that loop, your peak magnetic field drops by a factor of 4. You do not need 150kT to levitate a human. You just need a magnet that is physically larger with the same field strength and geometry.

One more thing. It's not just the magnitude of the magnetic field that controls whether something will levitate or not. The key is that the magnetic field gets weaker as you move up. Wikipedia [wikipedia.org] tells me that levitation power is proportional to B*dB/dZ. (the magnitude of the field times how quickly it diminishes as you move upward) That is to say, if you had a 150kT magnetic field, and it was constant everywhere, you wouldn't float in it.

Maybe near a neutron star you could find a proper spot to test this. Damn we need spaceflight - oh wait! Just getting into orbit costs you a few million whereas your big fat magnet costs what? Maybe you are better off with plain old free fall in an orbit or the vomit commet.

The dead squirrels did not seem to suffer adverse effects while they were levitating, though it must be said they were in this state only for a few moments and there were adverse effects after they struck their respective targets.

...using a 3-man slingshot and dead squirrels.
The dead squirrels did not seem to suffer adverse effects while they were levitating, though it must be said they were in this state only for a few moments and there were adverse effects after they struck their respective targets.

Dear sir or ma'am, I am a colleague of yours in the respected field of Airborne Necromancy and would like to see your records and raw data. Specifically I am interested to see trajectory and ballistics data on said deceased squirrel and would like to know targets, their reaction and splash radius (if any). Also, I require data on the haired appendage attached to the posterior of the squirrel and would like to know if it emitted a satisfactory trailing manifold while said furry body traveled along its arc. Also, if you have raw data on the reactions of homo sapiens of the homogametic sex upon realization of said ballistic squirrel, I would be eternally grateful for it and any footage of shear horror and/or terror. I look forward to peer reviewing your research in next month's issue of Bodies in Flight. Good day!

Dear eldavojohn - thank you very much for your interest in our research.

Unfortunately data collected on targetted facial responses is strictly limited to third-party hear-say information since the data collection stopped shortly after levitation was achieved due to personal safety risks to the research team if they were to have remained on-site. The time period of this research predates the "YouTube" era, and indeed no video recording devices were available that wouldn't prove too bulky for safe movement during the personnel evacuation window.

While my submission cannot be considered authoritative in this subject by peer review, it is refreshing to see other researchers interested in this field of study.

Refusal to relay your data to me?! I'll have you know I am the professor emeritus eldavojohn from Peter Wiggin's School for the Demented Brothers. Perhaps you've heard of it? Yes, well, I'm kind of a big deal there.

Your unwillingness to share crucial data to our pain-staking squirrel research not only upsets me but mars the very foundation upon which we have built our esteemed ideals and research. Furthermore your lack of savvy in the sub-field of post experiment egress and planning belie your innocence and naive dabbling in such a rewarding and rich genre of science.

In short, I recommend you put the squirrel slingshot down before you fail to hurt someone and leave the research to those of us properly equipped with chinchilla Gatling guns. Your work may make for a great show on the Discovery Channel but there's no place for you in my school.

While I cannot understand why you are so emphatic, I can empathize your position in this matter. We can expedite recreation of said research data and deliver it by air courier. Kindly prepare to receive a few drops presently, as soon as we fortify our research site with duct-taped cats and a tarp.

Dear sir or ma'am the squirrel rocket bomb is an ancient ritual performed during the new year festivals. It was used in EU in the '80 and '90. It consisted in putting a rocket petard inside a squirrel ass. The ritual eventually become banned, but the older people still remembers it.

But one must say, that levitation because of gravitational effects is not the same as that of (electro)magnetic effects. One can not use the one to study the other, for example. (Although some "scientists" attempt it nonetheless.)

Not sure about the squirrels, but others have great success putting Linux on dead badgers [strangehorizons.com]. That may be cross-compilable to squirrels, but you'd definitely need the memory stick version, just from space concerns.

So, wouldn't it generally levitating the mouse using the iron in its blood? So if your blood cells are yanking your body around, wouldn't that sort of interrupt the normal flow of blood and cause damage to the walls of your veins and capillaries and arteries and all that?

"The strong magnetic fields did not seem to have any negative impacts on the mice in the short term, and past studies have shown that rats did not suffer from adverse effects after 10 weeks of strong, non-levitating magnetic fields."

Sure, but put a cell phone next to their cage, and they have cancer in a week, right!?!

Cell phones operate at different frequencies and different power levels than the apparatus used in this experiment, so the lack of adverse effects on the mice does not really say anything about the effects of a cell phone on mice (or humans).

The field in this experiment isn't EM radiation at all. It's just a (really big) magnet. There is no time varying component (it has no frequency) so it does not have an electric component (look up Maxwell's equations). This has as much to do with EM radiation as a cup of water on your desk has to do with the waves on the ocean.

That said, if you move a wire through it, you'll generate one hell of an electic field, but only while the strength of the magnetic field through the wire is changing.

That said, if you move a wire through it, you'll generate one hell of an electic field, but only while the strength of the magnetic field through the wire is changing.

Wait, if you move a wire through an unchanging field (perpendicularly), you'll induce a current, right? You'll also induce one if you hold a wire still in a field whose strength is changing.

On a related note, axons are in many ways like long wires. Move around in a high magnetic field, and you'll notice odd effects. It's more of a problem for people than for mice -- our axons run longer, and so inductive effects are stronger.

Axons aren't quite like wires, though. Its been awhile, but don't they use current via ion channels, and not an actual current? When activated they suck up a bunch of positive ions (I think calcium, might be wrong though), and expel the negative ones (potassium, might be wrong though) creating a charge. They aren't llike little wires.

If they were, I imagine that MRI's would be much more interesting though.

Oh, but they do get interesting, if you disable the rate-of-field-change safeties that are integrated into clinical scanners. Our lab does high-resolution MR imaging in small animals, and if we don't disable those safeties, we can't get the gradients we need. (In this field, "gradient" refers to a varying magnetic field that's overlaid on the nominally constant and uniform field from the main magnet.)

Even without involving the gradients, if you move your head too quickly near the bore of our 7T magnet, it can have very odd effects. I'm not sure of the mechanism, but I've assumed it has to do with currents induced in axons. They aren't wires, but they are conductive channels, and as Volta showed, they do respond to purely electrical stimulation.

(I hope someone better versed in MR physics will chime in here. I'm just a lowly computer guy, relying on what I've soaked up from my co-workers due to curiosity and overheard discussions.)

Wait, if you move a wire through an unchanging field (perpendicularly), you'll induce a current, right? You'll also induce one if you hold a wire still in a field whose strength is changing.

A voltage is induced only when the magnetic flux (aka, the strength of the magnetic field) in the wire changes. If the wire is moving perpendicular to the field in such a way that the wire 'sees' a constant magnetic field strength (in theory), there will be no voltage. In practice this is very difficult to do (the wire will move at least a little bit).Per the definition you are correct that a time-varying magnetic field will also induce a voltage (this is how the secondary on a transformer works). Howeve

If the wire is moving perpendicular to the field in such a way that the wire 'sees' a constant magnetic field strength (in theory), there will be no voltage.

No, not the strength per se. If a moving wire crosses lines of [constant or varying] magnetic flux, a voltage is induced in it.

Example: imagine a large circular magnet with a narrow slot that forms a pair of parallel poles. The fiend strength in the central region of the poles is essentially constant (and perpendicular to the plane of the poles). I

All that is required is a change in flux, and a wire moving through a constant magnetic field is a change in flux. You can think of a 'change in area times field over time' as 'length times field times change in position over time'. The wiki page on Faraday's law of induction [wikipedia.org] shows how you arrive at the velocity-based component of induced emf.

On the other hand: Put them in a microwave and shoot them with a industrial-strength laser, and they will not have cancer too... because they will be a heap of ashes.

I understand your argument and I specifically agree with it. But by putting yourself in the opposite extreme position, you're not much better than them. Even if it happens for dubious humoristic purposes. ^^

Hmm, If I remember correctly from my physics class, any time electrons move through a magnetic field, don't they produce electric forces in a direction perpedicular to the motion through the magnetic field? Or something like that. Anyhow, electric generators, I remember, are just coils of wire that you rotate inside a strong magnetic field.

So, the question is, could exposure to magnetic fields strong enough to levitate you, also cause electric currents in your body, if you move through the field, strong eno

Hmm, If I remember correctly from my physics class, any time electrons move through a magnetic field, don't they produce electric forces in a direction perpedicular to the motion through the magnetic field?

An electrical current generates a magnetic field surrounding it. In the presence of another magnetic field, the two push against each other (as magnets do) and produce a physical force on the condustor.

And as TFA mentions, rats suffered no ill effects from long-term exposure to strong (probably several Tesla) magnetic fields. It is possible that intensely strong (hundreds or thousands of Tesla) could cause issues, though, but that's what research and experiments are meant to determine.

past studies have shown that rats did not suffer from adverse effects after 10 weeks of strong, non-levitating magnetic fields.

Right. Non-levitating has no negative effects in the short term. Actual Levitating has no immediate effects in the short term. The effects of levitating magnets in the long term could be catastrophic, and if thats the case I hope we observe it and know not to put ourselves through it.

However, we've seen first hand that astronaughts who don't get exercise in 0 gravity have had some side effects like Atrophy, so I hope they have zero gravity mouse wheels to keep these mice in shape while testing them for prol

so I hope they have zero gravity mouse wheels to keep these mice in shape while testing them for prolonged periods.

Where's your sense of imagination? If it's zero G, we're not limited to mouse wheels and/or hamster balls. How about a hamster tetrahedron? I mean, not to be one-sided, but surely a mouse mobius strip is the least we could hope for?

To be honest with you, when you reach this level of awesome in your experimentation, you don't even need a premise. The NASA scientists could have simply announced that they did it for the lulz and it would be okay.

Regarding gradients: The gradients used in MRI vary in *position*. Yes in time, as well, but only because they are pulsed. We can ignore ramping issues to first order. Since the field varies as a function of position, when you move around, indeed the flux is changing which can induce currents in looped conductors so as to oppose the change. This is called induction. Many people, my self included, notice a strange sensation when first entering an MRI magnet. This is because the field is only homogeneous over a relatively small volume, outside of which there are once again field gradients (these are different than the intentional field gradients used to obtain an MRI image). It is probably not axons but something in the ear that is picking this up, I am not sure. Also, field strength has *nothing* to do with this effect. It's how fast the field changes as a function of position, i.e. the gradient, combined with the velocity of the pickup object.

Regarding repulsion: Water is diamagnetic. That means that the little spins (i.e. electrons) orbiting the atoms of a water molecule tend to align *against* the applied field direction. These spins will experience a repulsive force, hence the levitation.

This is fine. Most people don't come here for breaking news, they come here for (sometimes) informative, enlightened, or humorous discussion of the article and related topics.

I'll just add that your griping is none of those things. If what you care about is being the first to read about something, then please feel free to go elsewhere. And feel free to not bother with the discussion on Slashdot when the same item is up a day or two later... you won't be missed if what you post is similar to the post I'm responding to.

Oh, and one last thing... Slashdot is a news aggregator. There is very, very little original content in the items posted to the main page. However, it is a community-driven site. If you're unhappy that items come through later here than elsewhere, one thing YOU can do to improve it is to submit articles yourself in a timely manner.